GB250747A - Improvements relating to high frequency electric signalling - Google Patents

Abstract

250,747. Braendle, E. W., and Metropolitan-Vickers Electrical Co., Ltd. March 31, 1925. Duplex signalling; wired-wireless systems. - A duplex high-frequency signalling system comprises a valve transmitter and an adjacent valve receiver with their plate circuits supplied by an A.C. source in opposite phase, so that the transmitter is operative during one half-cycle only, and the receiver during the other. The operative half-cycles of the distant transmitter coincide with those of the home receiver, and the home transmitter with the distant receiver. As shown in the Figure, a power distribution line 1, 2 energized by an alternator 3, is utilized for conveying the high-frequency signals, the transmitting valves 4, 20 and the receiving valves 10, 21 being electrostatically coupled to the line 2 at 8, 12 - - The plate potentials of the valves are supplied by the line 1, 2 in such a way that the valves 4, 21 have their plates positive during the same halfcycles, whilst during the other half-cycles, the valves 10, 20 have their plates positive. When the key of the valve 4 is depressed, the valve oscillates intermittently, and the oscillations trig the distant receiver 21 into oscillation and give an indication by means of a relay in the plate circuit. The home receiver 10 is not affected, as its plate is negative during the intermittent oscillatory periods of the valve 4. If a wireless transmission system is employed, two separate A.C. sources such as 3 are employed, and are kept in step by a synchronizing carrier wave. Transformers are preferably employed between the line 1, 2 and the plate circuits, and the filaments may also be energized from the line 1, 2.